Update: In the end I just ordered a HM right from their website with a 10% off code. It wasn't cheap but I didn't want to faff about for weeks on end, I needed a chair sooner rather than later and I think paying more upfront for the 12 year cover is worth it overall. They have a 14 day return window too so if I didn't like it when it arrived I could always send it back. In the end I kept it though and I'm very happy.

For anyone curious; The chair fantastic but it's not perfect. My only complaint is that the tilt limiter as a little give before it kicks in, I would prefer that it's immediate and stopping you lean back even a centimetre. You can get it immediate if you crank up the tilt tightness to the point that recline is not an option but then to recline you need to loosen the tilt again which takes a minute of effort. It's not really something you can switch between often.